> For some reason people are willing to produce design documentation....

I'm assuming you wrote that just for dramatic effect but let me explain why I think this behavior is completely rational.

If you implement "feature X" you already learned everything you needed, so adding documentation is a task that doesn't bring you any benefits. You could argue that it would make your life easier when you have to do some maintenance in this code, but that is a pretty big time investment for something you may use some day.

But now with LLMs that reasoning changes dramatically. Having good documentation makes your life easier right now. And the same argument can be made for every good practice that people never bothered to follow: commit messages, tests, variable naming, ...

For example, where I work the 'developer experience' team created a bot that reads your merge requests and judges your changes to understand if they are small enough to bypass the need to have an explicit approval from a coworker. And one of the things that it takes into account is how well documented is this change. If you have a small change without any context the bot won't approve your MR, but you explain the bug and add some relevant tests it will approve your MR and allow you to skip the human code review.

And the result of this new bot is that people are starting to better document their changes, because this allows them to work faster.

So, I agree with GP that is funny to see this play out. But it should not be a surprising behavior for anyone that understand how software is written.